I got the same problem and just called and spoke to tech support for StaRite/Pentair. They said that is a simple one. The Thermister is the unit failing. It is located to the left of the water inlet to the heater and is stuck open and needs to be replaced. They said more than likely that is the issue. If not, then call them back. I was only on hold for less than 10 min.
Answers & Comments
I got the same problem and just called and spoke to tech support for StaRite/Pentair. They said that is a simple one. The Thermister is the unit failing. It is located to the left of the water inlet to the heater and is stuck open and needs to be replaced. They said more than likely that is the issue. If not, then call them back. I was only on hold for less than 10 min.
Replacing the thermister solved the problem for me.